The present invention generally relates to centrifugal separators and more particularly relates to centrifugal oil filters for engine and vehicle applications.
Current heavy-duty diesel engines put a moderate amount of soot (a form of unburned fuel) into the oil pan. This soot is generated due to the fuel hitting the cold cylinder walls and then being scraped down into the oil sump when the pistons reciprocate in the cylinders. Up until recently, the nitrous oxide emission regulations in the United States and other countries have been high enough that the fuel injection timing could be such that the level of soot generated was not high. In typical applications, the soot level would be under 1% (by weight) of the engine oil at oil drain time. At these low levels, soot in the oil does not cause any significant wear problems.
Recently, there has been a move to significantly lower nitrous oxide emissions which requires much retarded fuel injection timing, which significantly increases the amount of soot being generated. At reasonable oil drain intervals, the soot level may be as high as 4 or 5% with retarded injection timing. When the soot level gets this high, lubrication at critical wear points on the engine becomes so poor that high wear results, significantly decreasing the miles to overhaul and causing high operator expense.
Thus, the engine manufacturer has two choices, suffer very high warranty costs and low miles to overhaul, or significantly lower oil drain intervals to keep high soot levels out of the oil. Neither of these choices is desirable, so there is a current strong need to have a means of getting the soot out of the oil, the subject of this invention.
A problem with removing the soot from oil is that it is very small in sizexe2x80x94around 0.1 to 2.0 micrometers. To remove such small particles from oil using barrier filtration is not feasible due to the large filter size required and the very high probability that the filter will become plugged very rapidly due to trying to filter to such a fine level.
One way that is feasible to remove the soot from the oil is by using a centrifuge, a device that removes the soot from the oil using centrifugal force. This type of device is used to separate blood constituents from blood and has many other applications in typical laboratory applications. The use of a centrifuge for an engine brings a requirement of doing it in a very inexpensive and reliable manner with the centrifuge being easily changed at oil change time. Heretofore, centrifugal filters have not been able to sufficiently remove soot from oil, sufficiently retain the soot, nor reliable enough for use in engine and vehicle applications.
In view of the foregoing, a primary objective of the present invention is to provide a practical and reliable centrifuge filter for filtering soot from engine oil in vehicle applications.
In that regard, it is an object of the present invention to drive a centrifuge rotor at sufficient speed using existing power supplies of a vehicle, and which also minimizes powering requirements.
In that regard, it is a further object of the present invention to provide adequate residence time and centrifugal force sufficient to filter soot from the oil.
In accordance with these and other objectives, the present invention is directed toward a novel centrifuge housing mounted in a vehicle and connected to the oil system of the vehicle""s engine in which air is evacuated from the rotor chamber to reduce the air drag on the rotor (and increase rotor speed or reduce power requirements). The centrifuge housing includes a sealed centrifuge rotor chamber providing an isolated environment in which the centrifuge rotor is supported for rotation. The housing has an inlet port connected to the engine to receive oil and an outlet port connected to the engine to return oil to the engine. To effect the partial vacuum in the rotor chamber, a venturi conduit is interposed between the inlet port and the outlet port. The venturi conduit has operatively larger and smaller flow capacity passage portions adapted to create suction via the venturi effect. The isolated atmosphere is fluidically connected to the venturi conduit wherein the suction creates a partial vacuum in the isolated environment of the sealed centrifuge rotor chamber for reduced air drag on the centrifuge rotor during rotation.
The present invention is also directed toward a novel method of centrifugally filtering soot from oil in an engine of a vehicle. The method comprises sealing the centrifuge rotor chamber to provide an isolated atmosphere in which the centrifuge rotates, rotating a centrifuge rotor inside a centrifuge housing to remove soot from oil, and evacuating air in the isolated atmosphere to provide a partial vacuum reducing air drag on the centrifuge rotor.